Heat exchangers are commonly used where heat produced a plant or a machine needs to be transferred away from the plant or machine. One very common type of heat exchanger uses one or more heat exchanging arrays each comprising a plurality of fluid conduits or tubes surrounded with fins (finned tubes) and arranged so that cooling fluid, such as air, water and the like (coolant), can flow over the tubes and dissipate their thermal energy. When a large amount of heat needs to be removed, the heat exchanger will typically be located outdoors. Some large heat exchangers are built to be cooled by air and are installed so that the desired flow of air through the heat exchanger is from the bottom up. In order to increase the rate of heat dissipation, fans can be installed above the heat exchanger to induce the flow of air from the bottom up through the heat exchanger. When cooling fluid flows through the heat exchanger, the mode of dissipation is convection. When the flow of coolant is stopped, the heat dissipation will be carried out mostly in a radiation mode which is much less efficient compared to the convection mode. Very large heat exchangers are typically arranged in a horizontal very long rectangle (ratio of length to width being very high). FIG. 1A shows heat exchanger 2 as is known in the art. Heat exchanger 2 may comprise finned tube section 4 and plurality of fans 6. Heat exchanger 2 has length L, width W and height H. Heat exchanger 2 is typically installed above the level of ground at a distance FH from the ground to allow free flow of air underneath the heat exchanger.
The efficiency of heat dissipation of such heat exchangers depends on various ambient conditions and changes therein, such as the amount of exposure to direct sun light, the ambient temperature and the actual wind (direction and magnitude) at the heat exchanger location. For large heat exchangers with a high aspect ratio (L/W) figure, wind blowing parallel to its length dimension has a negligible effect. In contrast, wind blowing parallel to its width dimension may have a substantial effect.
With strong enough winds flowing over a heat exchanger parallel to its width dimension, the flow of coolant air through the heat exchanger may be disturbed and even completely blocked, as can be seen in FIGS. 1B and 1C, schematically depicting cross section 10 in heat exchanger 2 partially along cross section line AA, showing only one fan and its finned tube section 11 [section plane SF(P)]. The air flow through heat exchanger 10 when no wind blows can be seen from FIG. 1B while the air flow through heat exchanger 10 when wind blows from right to left can be seen from FIG. 1C. As may be seen, when no wind blows over heat exchanger 10, the air flow produced by fans 12, through finned tubes section 11, is undisturbed and evenly distributed across the exchanger from right to left. However, when wind blows across heat exchanger 10, as seen in FIG. 1C, the coolant flow through the portion of exchanger 10 that is close to the wind side is disturbed. FIG. 1D is a graph depicting the amount of air flow through each one of three fans F1, F2 and F3 ordered in row 20 in an array across the width dimension of a heat exchanger such as heat exchanger 2 (FIG. 1A). F1 is the fan closest to the wind side. The graph of FIG. 1D presents the amount of mass of air, [kg/Sec], (Y axis) flowing through each fan as a function of the wind speed [m/sec] (X axis) blowing parallel to the width dimension. While the changes in mass flow through F3, which is farthest from the wind side, as function of the wind speed, are negligible, the mass flow through F1, the fan closest to the wind side drops down sharply with the wind speed and equals to half its maximum at 45 msec. (about 160 km/h) and to zero at wind speed of 70 m/sec. (about 250 km/h). FIG. 1E represents the temperature distribution in the air above fans F1, F2 and F3 when strong wind blows over the heat exchanger from right to left. It can be seen that the air above fan F1 reaches only the lowest temperature, meaning that the capability of F1 to remove heat is minimal. As opposed to fan F1, above fan F3, the fan farthest from the side of the wind, there is a high column of air with the highest temperature, indicative of high capability of heat dissipation. Note that temperatures of the heat exchanger itself are not reflected in this drawing.
There is a need for a solution that will minimize the dependency of the operation of a heat exchanger of the known art on the wind.